Marla Bay algae could reflect an increased impact on South Shore |

Marla Bay algae could reflect an increased impact on South Shore

Nobody knows for sure what has caused Marla Bay to sprout green algae, but experts agree the slimy stuff is an unwelcome intruder.

The algae, from the genus Zygnema, has been found in the bay’s shallow water in unprecedented levels this summer. Why the bloom has settled mainly in Marla Bay – just south of Zephyr Cove – and what factors pinpointed it to this area have local scientists scratching their heads.

“It’s a very open question,” noted Geoffrey Schladow, director of the Tahoe Environmental Research Center of the University of California, Davis.

Schladow and other researchers want to know if nutrients are fueling Zygnema’s growth by infiltrating the bay with nitrogen and/or phosphorus. To that end, scientists began gathering water samples this week that will be analyzed to identify what’s causing the algae to grow. Results could take several weeks.

The situation has become acrimonious: Some Marla Bay residents and the Tahoe Area Sierra Club believe the bloom has resulted from widespread development at the lake and inadequate managing to prevent intrusion of invasive species.

“It’s just symptomatic of what’s going on around the lake,” said Michael Donahoe, local Sierra Club conservation co-chairman. “We’re not winning this battle right now, and we don’t seem to have the collective will to address the issues.”

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Much of the onus of keeping Lake Tahoe pristine falls on the Tahoe Regional Planning Agency. Despite the current controversy, the TRPA defends its environmental measures to reduce harmful impacts to the lake.

Said TRPA spokesman Dennis Oliver: “All indications are the 10 years of EIP (Environmental Improvement Program) and some of the BMP (Best Management Practices) compliance work in the basin has helped us turn the corner in terms of water quality and lake clarity.”

Oliver speculated that high fecal counts in the water near Marla Bay could potentially be feeding the algae. Horse manure running into the bay or a possible sewer leak might account for the high counts, he added. TRPA staff also contend that a combination of factors – including low lake level, warm temperatures or increased fertilizer use in the area that drains into Marla Bay – could be causing the bloom.

Scientists also want to examine a possible relationship between the algae and Asian clams, which likely have been in the lake since 2002. The clams could be creating pockets of water with relatively high calcium concentrations favorable to invasive mussel growth.

The obvious conclusion to all of this won’t surprise anyone: Researchers must determine what’s causing the bloom and halt it at the source. That’s no easy task, considering the number of variables they must examine.

Development, tourism and natural disasters such as forest fires continually affect the quality of the lake.

Oliver is correct: Over the past decade and longer, the TRPA and other basin environmental organizations have initiated successful programs to help keep our area as healthy as possible.

Continued vigilance and camaraderie is the key. Finger-pointing accomplishes nothing.